This represents a 65-percent growth year-over-year. According to eMarketer analyst Noah Elkin, the ad spending calculation this year is adjusted only slightly higher, but the forecast for coming years has been revised more substantially, Media Post reported.

The ad spending is expected to up 47 percent to $1.8 billion in 2012, and up 40 percent to $2.5 billion. In 2014, there will be another 34-percent expansion to $3.4 billion and a 30-percent rise to $4.4 billion in the year ahead.

“The increased outlook reflects steeper smartphone and tablet adoption over the forecast period,” Elkin said. “Simply put, these factors are making the Web more mobile and more of an imperative for marketers.”

eMarketer also pointed out a considerable shift in share of spending among the major channels in the next several years. This year, messaging owns the largest share at 36.1 percent, but it is estimated to shrink to only 14.4 percent by 2015.

Search, which made up 28.5 percent of spending now, is set to reach 40.2 percent, and banners and rich media will expand from a 30.7-percent share to 36.4 percent by 2015. Video, although only accounting for 4.7 percent, will grow fast to 9 percent, with the compound annual growth rate of 69 percent between 2010 and 2015, eMarketer reported.